What is a Capacitor and Why do I need one?What is that and why do I need one?
A capacitor is a secondary storage device for electrical power. This is installed inline between the vehicles battery and close to the amplifier it is supposed to help supply power to.  They will have positive and negative terminals and some type of LED display for voltage reading. They may come in the form of a cylinder tube style (PCBLK3.5  3.5 Farad Capacitor with Digital Voltage Display) or in a block form (Planet Audio PC10F Super Hybrid 10 Farad Power Capacitor). They will of course have the installation mounting hardware and charging instructions.

So your lights at night are dimming when you play your music at high volumes?
When your music is at high volumes and the bass is hitting hard, the amplifier is pulling current from the alternator and that puts a strain on the alternator. Your vehicles alternator is designed for the electronics in your vehicle and was not designed to supply a rapid demand of current from aftermarket amplifiers. And let’s not forget the OEM battery for your vehicle. That was designed to start your vehicle and not for aftermarket electronics such as a multi amp audio system.  When a stiffing capacitor is used it is providing the gap in the current flow that is lost during the charging output of the alternator. This may not always fix the dimming problem, as there are other issues that must be addressed.
  1. Improper wire gauge
  2. Multiple grounds points in the vehicle. Also leads to noise in the system (ground loops).
  3. Loose connections and or corroded terminals on the battery
  4. Old or weak battery
  5. Battery has a dead cell
  6. Factory alternator
  7. Alternator is defective, too little output or overcharging
  8. Multiple power wires that are of different size and lengths
  9. Excessive accessories
  10. Lack of the “big 3 upgrades” (Video on YouTube)
Most of the above mentioned can be maintained by the owner and or audio installation center. And you will see the vast improvement the capacitor will bring to your electrical system. Alleviating the strain on the factory charging system. For best results from your audio system, upgrade the factory battery to deep cycle battery and upgrade to a high output alternator.